#include<stdio.h>
int Fib(int n) {
	if (n <= 2) {
		return 1;
	}
	else {
		return Fib(n - 1) + Fib(n - 2);
	}
}
int main() {
	int n = 0;
	scanf_s("%d", &n);
	printf("%d\n", Fib(n));
	return 0;
}